1. Field of the Invention
The present invention generally relates to a method of fabricating electronic parts packaged with resin and a baseboard suitably used for the method.
2. Description of the Related Art
Recently, there has been a demand to downsize electronic parts mounted to electronic devices and improve the performance thereof with downsizing and higher performance of the electronic devices. For instance, there have been similar demands on surface acoustic wave (SAW) devices that are electronic parts used as filters, delay lines, oscillators in electronic devices capable of transmitting and receiving radio waves.
Generally, SAW devices have a SAW filter chip that is flip-chip mounted within a cavity having a bottom surface on which interconnection lines are formed. An interdigital transducer having comb-like electrodes is formed on a piezoelectric substrate of the SAW filter chip. This type of SAW devices is disclosed in Japanese Laid-Open Patent Application Publication No. 2001-53577, particularly, FIG. 3.
The SAW device of the above-mentioned type may be fabricated as shown in FIGS. 1 and 2 in which FIG. 2 is a cross-sectional view taken along a line A—A shown in FIG. 1. Multiple SAW devices 111 are produced on a single baseboard 110. The baseboard 110 is divided into separate SAW devices 110 by a laser beam or dicing blade. The fabrication process of this type, which is described in, for example, Japanese Laid-Open Patent Application Publication No. 2001-110946, particularly, FIG. 7, results in many SAW devices at a time.
More specifically, cavities 115 are two-dimensionally arranged on the baseboard 110. The bottoms of the cavities 115 are metallized to form electrode pads 116 for bumps 114. A wiring board 130 is provided on the bottom of the baseboard 110. The SAW filter chips 113 are bonded to the electrode pads 116 in the facedown state by bumps 114. A resin sheet 112 is placed on the entire surface of the baseboard 110. Then, the baseboard 110 is divided into the separate SAW devices 111 that are hermetically sealed with resin. The productivity and cost can be improved by mounting the SAW devices 111 as many as possible.
However, the conventional fabrication method has the following disadvantages. In the process of sealing the baseboard 110 with the resin sheet 112, resin may deeply enter into the cavities 115 located at the outermost positions of the two-dimensional arrangement. The resin that deeply enters into the cavities may degrade the filter characteristic and environmental capability of the SAW devices 111. The faulty SAW devices 111 thus produced may not be shipped. If the resin comes into contact with the comb-like electrodes, the SAW devices 111 are absolutely defective. Many SAW devices located at the outermost positions may be defective, so that the production yield reduces and the cost increases.